New Therapy for Myasthenia Gravis

Rozanolixizumab is now available on the Pharmaceutical Benefits Scheme (PBS) for the treatment of generalised myasthenia gravis. Myasthenia gravis is an autoimmune disorder characterised by fluctuating muscle weakness and fatigability.

Rozanolixizumab is a monoclonal antibody that blocks the neonatal Fc receptor (FcRn). FcRn normally protects immunoglobulin G (IgG) antibodies and albumin from intracellular degradation, thereby extending their circulating half-life. By preventing FcRn from salvaging and recycling IgG antibodies, rozanolixizumab promotes their lysosomal degradation. This rapidly reduces the levels of circulating IgG, including pathogenic autoantibodies.

Rozanolixizumab is administered as a subcutaneous infusion. In the Phase 3 MycarinG trial, patients were randomly assigned to receive weekly infusions of rozanolixizumab 7 mg/kg, rozanolixizumab 10 mg/kg, or placebo for six weeks. The primary efficacy endpoint was change from baseline in the Myasthenia Gravis Activities of Daily Living (MG-ADL) score. Higher scores indicate greater disability and a reduction of at least 2 points is generally considered clinically meaningful. Mean reductions in MG-ADL score were greater with rozanolixizumab 7 mg/kg (-3.37) and 10 mg/kg (-3.40) than with placebo (-0.78).

The most commonly reported adverse effects were headache, diarrhoea, and pyrexia. While formal drug interaction studies have not been conducted, rozanolixizumab is expected to affect IgG-based therapies. If intravenous immunoglobulin (IVIg) or monoclonal antibody therapies are required, it is recommended that they be initiated at least two weeks after a rozanolixizumab infusion and that patients be monitored for reduced therapeutic efficacy.